Area Forecast Discussion
Issued by NWS Wilmington, NC-- Remove Highlighting --
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FXUS62 KILM 261007
Area Forecast Discussion
National Weather Service Wilmington NC
610 AM EDT Mon Sep 26 2016
A stalled front will waver across the area today. A stronger cold
front will approach Wednesday before slowly crossing the area
through late in the week although timing of this front is highly
uncertain. Cooler and drier weather is expected by the weekend.
.NEAR TERM /THROUGH TONIGHT/...
As of 330 AM Monday...Progressive flow aloft and at the sfc this
period as witnessed by all models which are in general in good
agreement for this period. The eastward moving mid- level ridge
axis pushes overhead today...and east of the FA tonight. Some
bagginess or weak troffiness upstairs, underneath this ridge, has
lagged behind across the SE U.S. States this past weekend and into
this period. A mid-level trof closes off across the western Great
Lakes by late today, and further deepens as it drops to the
Central Great Lakes by daybreak Tue. In essence, the U.S. east of
the Mississippi River is now under the influence of this upper
closed low. Not quite a cut-off due to the upper westerlies are
still pushing thru this upper feature.
Model are in good agreement with movement of sfc features this
period. A 1025mb centered sfc high over New England this morning,
will ridge across the Carolinas into Ga today. The center of this
high pushes off the New England coast and drops SSE to the
offshore waters from the Mid-atlantic states tonight but still
continues to ridge back across the previously mentioned states. An
inverted sfc trof develops just offshore and parallel to the ILM
CWA coastline tonight. And by Tue daybreak, a cold front
associated with the expansive closed low, dropping SE and reaching
the western Carolinas late tonight.
Initially, the ILM CWA will have to deal with the bkn-ovc stratus
deck at 2k to 3k feet this morning. This deck will become sct-bkn
later today and tonight. As for POPs today, with little or no
progged instability until late tonight, have decided to keep POPs
out of the forecast for daylight Mon. This shown by the latest
RAP and HRRR models. For tonight, will indicate a slow increase in
POPs as the inverted trof offshore develops, along with a weak sfc
low off SC/GA coasts from the dynamics associated with the
bagginess aloft discussed earlier. POPs from this feature and also
increasing POPs from the approaching cold front will be advertised
across the FA. Via latest RH model time height displays across the
FA, plenty of mid and upper level dry air today will mix with the
lower levels and partially scour out some of this low level
stratus. Thus, have stayed close to a consensus for the max/min
temp model mos guidance...with an emphasis of slightly hier, by 1
to 2 degrees, for todays highs.
.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 400 AM Monday...Amazingly, the models have the general idea
of a closed low dropping south from the Great Lakes and becoming
a cutoff low by the end of this period, with the westerlies
bypassing this upper low by the end of this period. Like spokes on
a bicycle, weak mid-level vorts or S/w trofs, rotating around the
upper low, will occasionally affect the FA this period. More-so
when this upper low drops to the central Appalachians. These
s/w`s will be able to interact with dynamics from the slow moving
sfc cold front moving/slithering across the FA. POPs will be
advertised each day, likely hiest during Tue due to the passage of
the sfc low along the inverted sfc trof just off the coast. With
the cold pool aloft partially reaching the area during the latter
half of this period, increasing the lapse rates and instability,
especially involving the days insolation, the chance for
thunderstorms will exist thruout this period. Leaned toward the
European MOS Guidance over the GFS Mos due to its recent slightly
better performance over the GFS Mos.
.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 300 AM Monday...Big differences in the extended continue to
cause lowered confidence for late this week. While the guidance all
shows a deep trough closing off across the OH VLY, the evolution
thereafter becomes quite muddled. The ECM continues to be a
strong/slow/west outlier with this feature as it digs into the lower
Appalachians and then actually retrogrades to the NW through
Saturday before finally ejecting late in the wknd. The GFS/CMC are
more in line with a sharp digging through Thursday and then lifting
off to the NE through New England Friday and into the wknd. Although
the ECM has been consistent the last few days, the GFS solution is
still preferred as a retrograde west of the upper low into a +3 SD
ridge seems unlikely. WPC cannot rule out any solution at this time
however, so a blended forecast is preferred with highest weight on
This upper low will determine the passage of a surface cold front
which continues to slow in forecast guidance. Favoring the GFS,
FROPA is now expected early Thursday, with cool and dry weather
expected Fri-Sun. In fact, temps Fri-Sun may fall slightly below
climo for both highs and lows as the first fall-like airmass of the
season advects into the Carolinas beneath Canadian high pressure.
Will note that if the ECM solution verifies, the front won`t cross
until Saturday, leaving much more unsettled weather through the
week, along with continued above normal temperatures.
.AVIATION /12Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --As of 12Z...A washed out front will remain nearly stationary and
dissipate today. Predominately easterly flow, a bit more
northeasterly early on. There will be quite a bit of a high stratocu
deck this morning, more scattered by this afternoon. Tonight some
fog entering the picture well after midnight, mainly inland.
EXTENDED OUTLOOK...Chance for SHRA/TSRA each day through
Wednesday, with morning fog/stratus also possible. VFR Thursday
-- End Changed Discussion --
NEAR TERM /THROUGH TONIGHT/...
As of 330 AM Monday...Small craft exercise caution thresholds will
be flirted with today, mainly across the waters from Cape Fear
Sfc ridging to persist across the local area, extending from the
highs 1025 mb center, in transit from New England to offshore
from the Mid-Atlantic states by Tue daybreak. By Tue morning,
models indicate an inverted sfc trof parallel and offshore from
the Carolina coasts. In all, this means a continued onshore wind
trajectory and with a semi-tightened sfc pg, wind speeds will run
around 15 kt with possible gusts up to 20 kt today, dropping to
10-15 kt tonight. Significant seas will run 2 to 4 ft thru
tonight, except a solid 3 to 4 ft north of Cape Fear and also
south of Murrells Inlet. Both locations away from the influence of
Frying pan Shoals. Wind waves at 4 to 6 periods will dominate with
an underlying 1 to 2 foot ese ground swell at 9 to 10 second
SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 400 AM Monday...Will see a veering trend to the winds from
easterly at the start of this period, to south southwest by the
end of this period. Weak sfc low to move along the inverted sfc
trof Tue. The sfc cold front to drop SE at a snail`s pace this
period, reaching the local waters by Thu morning. Wind speeds may
become temporarily northerly up to 15 kt after the low passes by
early wed, otherwise looking at around 10 kt for speeds with the
sfc pg relaxing up until the sfc cold front reaches the coast.
Significant seas will run 2 to 3 ft, possibly and briefly
up to 4 ft at the start of this period due to the passage of the
sfc low. Wind driven waves to dominate thru early Wed with
periods running 4 to 6 seconds. ESE, 1 to 2 foot ground swell
at 9 second periods will become dominate later Wed into early
LONG TERM/THURSDAY THROUGH FRIDAY/...
As of 300 AM Monday...Still some uncertainty in the extended with
respect to a frontal passage, but attm expect FROPA to occur
Thursday with W/SW winds around 10 kts becoming NW late. High
pressure will build in behind this front creating a very weak
pressure gradient, so winds across the waters on Friday will
feature highly variable direction with speeds of 5-10 kts. Seas of
2-3 ft Thursday will fall to around 2 ft on Friday thanks to the
weaker winds, and a continuing 2ft/9-10 sec SE swell.